CN117986460A

CN117986460A - Gel polymer, battery and preparation method thereof

Info

Publication number: CN117986460A
Application number: CN202410211230.6A
Authority: CN
Inventors: 肖智贤; 曹志锋
Original assignee: Shenzhen Heyi New Energy Technology Co ltd
Current assignee: Shenzhen Heyi New Energy Technology Co ltd
Priority date: 2024-02-27
Filing date: 2024-02-27
Publication date: 2024-05-07

Abstract

The application belongs to the technical field of electrolyte, and particularly relates to a gel polymer, a preparation method of the gel polymer, a polymer solid electrolyte and a battery. The gel polymer provided by the application comprises a polymer gel skeleton, lithium salt and an initiator, wherein the volume ratio of the polymer gel skeleton to the lithium salt is 1: (0.2-9) copolymerizing an unsaturated ester monomer and an oligomer monomer; the polymer gel skeleton formed by the method has rich ether chain segments and ester chain segments, so that the gel polymer provided by the application can have higher ionic conductivity, lithium ion migration number and electrochemical stability window at room temperature when being used as polymer solid electrolyte. The good chemical stability of the interface and the uniform and stable solid electrolyte interface layer are beneficial to improving the interface compatibility with metal lithium, effectively preventing the growth and infiltration of lithium dendrites and the occurrence of dead lithium, and promoting the uniform deposition of lithium.

Description

Gel polymer, battery and preparation method thereof

Technical Field

The application relates to the technical field of electrolyte, in particular to a gel polymer, a battery and a preparation method thereof.

Background

Lithium batteries have attracted extensive research interest in the development of large-scale energy storage devices such as electric vehicles and smart grids. The electrolyte is a key part of the lithium battery, and the physical and chemical properties of various components in the electrolyte play an important role in improving the performance of the battery. Among them, liquid electrolytes have been widely used because of their excellent conductivity and wettability and high electrolyte/electrode contact area. However, uncontrolled growth of lithium dendrites and the resulting "dead" lithium limit the use of liquid electrolytes in lithium metal batteries.

The solid state electrolyte can fundamentally change the behavior of lithium deposition. Currently, the polymer solid electrolyte widely used mainly includes: (1) The polyethylene oxide electrolyte has higher stability, but the polymer solid electrolyte has the problems of poor ion conductivity and low lithium ion migration number at room temperature. (2) The polyester-based electrolyte has better compatibility with lithium negative electrode and wider electrochemical stability window, but the poor ionic conductivity (10 ^-7 S/cm ~10^-5 S/cm) of the polyester-based electrolyte also limits the wide application.

Disclosure of Invention

Based on this, the application provides a gel polymer, a battery and a preparation method thereof. When the gel polymer provided by the application is used as a polymer solid electrolyte, the gel polymer can have higher ionic conductivity, lithium ion migration number and electrochemical stability window at room temperature.

In a first aspect of the present application, there is provided a gel polymer comprising a polymer gel backbone, a lithium salt and an initiator, the polymer gel backbone having a ratio by volume of 1: (0.2-9) cross-linking and copolymerizing an unsaturated ester monomer and an oligomer monomer;

wherein the unsaturated ester monomer comprises one or more of ethylene carbonate, methyl methacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, bis (trimethylolpropane) tetraacrylate, trimethylolpropane trimethacrylate, tetraethylene glycol diacrylate, pentaerythritol tetraacrylate and 2-phenoxyethyl acrylate;

the oligomer monomer comprises one or more of polyethylene glycol methyl ether acrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polyethylene glycol dimethyl ether and polyethylene glycol divinyl ether.

In one embodiment, the unsaturated ester monomers include one or more of ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, bis (trimethylolpropane) tetraacrylate, trimethylolpropane trimethacrylate, tetraethyleneglycol diacrylate, pentaerythritol tetraacrylate, and 2-phenoxyethyl acrylate.

In one embodiment, the oligomeric monomer includes one or more of polyethylene glycol methyl ether acrylate and polyethylene glycol divinyl ether.

In one embodiment, the polymer gel backbone has a ratio of 1 by volume: and (3) cross-linking and copolymerizing the unsaturated ester monomer and the oligomer monomer of (1-9).

In one embodiment, the number average molecular weight of the oligomer monomer is 200-6000.

In one embodiment, the lithium salt comprises one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium bis (trifluoromethane) sulfonimide, lithium bis (pentafluoroethyl) sulfonimide.

In one embodiment, the initiator comprises one or more of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, bislauroyl peroxide, and bis (4-t-butylcyclohexyl) peroxydicarbonate.

In one embodiment, the mass fraction of the initiator in the gel polymer is 0.1% -3%.

In one embodiment, the gel polymer further comprises an organic electrolyte.

In one embodiment, the organic electrolyte includes one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, 1, 2-dimethoxyethane, 1, 3-dioxolane, and succinonitrile.

In one embodiment, the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer monomer to the volume of the organic electrolyte is (1 to 3): (0.1 to 5).

In a second aspect of the present application, there is provided a battery comprising a positive electrode, a separator and a negative electrode, and an electrolyte filled in the gaps between the positive electrode, the separator and the negative electrode, wherein the electrolyte is the gel polymer according to any one of the embodiments of the first aspect of the present application.

In a third aspect of the present application, there is provided a method for manufacturing a battery according to the second aspect of the present application, comprising the steps of:

mixing the unsaturated ester monomer, the oligomer monomer, the initiator and the lithium salt to prepare the precursor solution;

assembling the positive electrode, the negative electrode, and the separator; injecting the precursor solution to assemble the battery cell;

Polymerizing the battery core at 40-80 ℃ to crosslink and copolymerize the saturated ester monomer and the oligomer monomer to form a polymer gel skeleton, so as to generate the gel polymer.

In one embodiment, the molar concentration of the lithium salt in the precursor solution is 0.5mol/L to 10mol/L.

In one embodiment, the precursor solution further includes an organic electrolyte; the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer monomer to the volume of the organic electrolyte is (1-3): (0.1 to 5).

The gel polymer provided by the application comprises a polymer gel skeleton, lithium salt and an initiator, wherein the volume ratio of the polymer gel skeleton to the lithium salt is 1: (0.2-9) copolymerizing an unsaturated ester monomer and an oligomer monomer; the polymer gel skeleton formed by the method has rich ether chain segments and ester chain segments, on one hand, the ether chain segments can effectively improve the lithium ion conveying capacity and reduce the ohmic polarization of the lithium metal battery; on the other hand, lithium ions can couple/decouple with oxygen in c=o, contributing to an improvement in ion conductivity.

In addition, the application limits the ratio of unsaturated ester monomers to oligomer monomers, and can limit the number of ether groups and ester chain segments in the polymer gel skeleton so that the polymer gel skeleton has higher dielectric constant and stronger electron withdrawing capability, and further can limit the movement of anions, promote the transfer of lithium ions and obtain higher migration number of lithium ions. This is advantageous for uniform deposition of lithium ions, suppresses uncontrollable side reactions on the electrode, and ensures uniform and stable formation of the solid electrolyte interface layer.

Therefore, when the gel polymer provided by the application is used as a polymer solid electrolyte, the gel polymer can have higher ionic conductivity, lithium ion migration number and electrochemical stability window at room temperature, and the good interfacial chemical stability and uniform and stable solid electrolyte interface layer are beneficial to improving the interfacial compatibility with metal lithium, effectively preventing the growth and permeation of lithium dendrites and the occurrence of dead lithium, and promoting the uniform deposition of lithium. The gel polymer has a unique cross-linked network structure, has good heat resistance and mechanical property, and ensures the safety of the battery. In addition, the in-situ polymerization mode is favorable for obtaining stable electrode/electrolyte contact and reducing the interface impedance of the lithium battery.

Detailed Description

The gel polymer, the battery and the preparation method thereof according to the present application will be described more fully and clearly with reference to the following examples. The present application may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

Herein, "one or more" refers to any one, any two, or any two or more of the listed items.

In the present application, "first aspect," "second aspect," "third aspect," "fourth aspect," "fifth aspect," etc. are for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity, nor as implying an importance or quantity of technical features indicated. Also, "first," "second," "third," "fourth," "fifth," etc. are for non-exhaustive list of descriptive purposes only and are not to be construed as limiting the number of closed forms.

In the application, the technical characteristics described in an open mode comprise a closed technical scheme composed of the listed characteristics and also comprise an open technical scheme comprising the listed characteristics.

In addition, for numerical ranges in this disclosure, it is understood that each intermediate value between the upper and lower limits of the ranges is also specifically disclosed. Every smaller range between any stated value or stated range, and any other stated value or intermediate value within the stated range, is also encompassed within the application. The upper and lower limits of these smaller ranges may independently be included or excluded in the range. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.

The percentage content referred to in the present application refers to mass percentage for both solid-liquid mixing and solid-solid mixing and volume percentage for liquid-liquid mixing unless otherwise specified.

The percentage concentrations referred to in the present application refer to the final concentrations unless otherwise specified. The final concentration refers to the ratio of the additive component in the system after the component is added.

The temperature parameter in the present application is not particularly limited, and may be a constant temperature treatment or a treatment within a predetermined temperature range. The constant temperature process allows the temperature to fluctuate within the accuracy of the instrument control.

A typical in situ polymerization process is to mix a monomer, an initiator, and a lithium salt to form a precursor solution; and then injecting the precursor solution into the battery during the assembly of the battery, fully wetting the electrode by the precursor solution, and then carrying out in-situ polymerization under certain external conditions to obtain the gel/solid polymer electrolyte.

In the prior art, a vinylene carbonate monomer, an azodiisobutyronitrile initiator and lithium difluorooxalate borate are mainly adopted as precursor solutions, so that in-situ polymerization is initiated by heat at high temperature, and in-situ generated solid electrolyte is uniformly fused into pores of a cellulose non-woven fabric membrane to form an interconnecting lithium ion transport channel. The polymer electrolyte has good electrochemical stability, but relatively poor ionic conductivity, and the ionic conductivity is only 0.022 mS/cm at room temperature.

Based on this, in a first aspect of the present application, there is provided a gel polymer comprising a polymer gel backbone, a lithium salt and an initiator, the polymer gel backbone having a ratio by volume of 1: (0.2-9) cross-linking and copolymerizing an unsaturated ester monomer and an oligomer monomer;

The gel polymer provided by the application comprises a polymer gel skeleton, lithium salt and an initiator, wherein the volume ratio of the polymer gel skeleton to the lithium salt is 1: (0.2-9) cross-linking and copolymerizing an unsaturated ester monomer and an oligomer monomer; the polymer gel skeleton formed by the method has rich ether chain segments and ester chain segments, on one hand, the ether chain segments can effectively improve the lithium ion conveying capacity and reduce the ohmic polarization of the lithium metal battery; on the other hand, lithium ions can couple/decouple with oxygen in c=o, contributing to an improvement in ion conductivity.

In addition, the application limits the ratio of unsaturated ester monomers to oligomer monomers, and can limit the number of ether groups and ester chain segments in the polymer gel skeleton so that the polymer gel skeleton has higher dielectric constant and stronger electron withdrawing capability, and further can limit the movement of anions, promote the transfer of lithium ions and obtain higher migration number of lithium ions. This is advantageous for uniform deposition of lithium ions, suppresses uncontrollable side reactions on the electrode, and ensures uniform and stable formation of the solid electrolyte interface layer. Therefore, when the gel polymer provided by the application is used as a polymer solid electrolyte, the gel polymer can have higher ionic conductivity, lithium ion migration number and electrochemical stability window at room temperature. The good chemical stability of the interface and the uniform and stable solid electrolyte interface layer are beneficial to improving the interface compatibility with metal lithium, effectively preventing the growth and infiltration of lithium dendrites and the occurrence of dead lithium, and promoting the uniform deposition of lithium.

It will be appreciated that the volume ratio of unsaturated ester monomer to oligomeric monomer may be selected from 1: (0.2-9). Specifically, the volume ratio of unsaturated ester monomers to polymer monomers includes, but is not limited to 1：0.2、1：0.4、1：0.5、1：0.8、1：1、1：1.1、1：1.5、1：1.7、1：2、1：2.5、1：2.8、1：2.9、1：3、1：3.1、1：3.5、1：3.8、1：4、1：4.1、1：4.5、1：5、1：5.5、1：5.8、1：6、1：7、1：8 or 1:9.

Preferably, the unsaturated ester monomer comprises ethoxylated trimethylolpropane triacrylatePropoxylated trimethylolpropane triacrylateBis (trimethylolpropane) tetraacrylate/>Trimethylolpropane trimethacrylate/>Tetraethyleneglycol diacrylatePentaerythritol tetraacrylateAnd 2-Phenoxyethyl acrylate/>One or more of the following.

Preferably, the oligomer-based monomer includes one or more of polyethylene glycol methyl ether acrylate and polyethylene glycol divinyl ether.

In one example, the polymer gel backbone has a ratio of 1 by volume: and (3) cross-linking and copolymerizing the unsaturated ester monomer and the oligomer monomer of (1-9). By further limiting the volume ratio of the unsaturated ester monomer oligomer monomer, the unsaturated ester monomer and the oligomer monomer are crosslinked to form a gel polymer with a three-dimensional network structure, and the three-dimensional network structure can provide more ion transmission channels so as to promote rapid movement of ions, thereby improving the ion conductivity of the electrolyte; in addition, the three-dimensional network structure is formed at the moment, and the three-dimensional network structure has rich pore structures, so that the pore structures can provide larger surface area, the contact area between lithium ions and electrolyte is increased, and the migration capability of the lithium ions is further enhanced.

In one example, the oligomeric monomer includes polyethylene glycol methyl ether acrylatePolyethylene glycol diacrylate/>Polyethylene glycol dimethacrylate/>Polyethylene glycol dimethyl etherAnd polyethylene glycol divinyl ether/>One or more of the following. The number average molecular weight of the oligomer monomer is 200-6000. It will be appreciated that the number average molecular weight of the oligomer-based monomer may be selected from any number between 200 and 6000. Specifically, the number average molecular weight of the oligomer-based monomers includes, but is not limited to, 200, 220, 240, 250, 260, 300, 350, 380, 400, 420, 500, 550, 600, 800, 1000, 2000, 3400, 6000. The number average molecular weight of the preferable oligomer monomer is 200-2000, and the oligomer monomer meeting the requirement can ensure the number of ether bonds and ester groups in a polymer chain so as to improve ion transmission and further improve the ion conductivity of the gel polymer; meanwhile, the low molecular weight oligomer monomer can increase the plasticity and deformability of the polymer chain, thereby improving the mechanical flexibility of the gel polymer.

In one example, the lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium bis (trifluoromethane) sulfonyl imide, lithium bis (pentafluoroethyl) sulfonyl imide, and lithium.

In one example, the initiator includes one or more of azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, benzoyl peroxide, bislauroyl peroxide, and bis (4-t-butylcyclohexyl) peroxydicarbonate.

The initiator can catalyze unsaturated ester monomers and oligomer monomers to crosslink and copolymerize, and can adjust the rate and strength of polymerization reaction. In one example, the mass fraction of the initiator in the gel polymer is 0.1% -3%. Specifically, the mass fraction of initiator in the gel polymer includes, but is not limited to, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8, or 3%.

In one example, the gel polymer further comprises an organic electrolyte.

In one example, the organic electrolyte includes one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, 1, 2-dimethoxyethane, 1, 3-dioxolane, and succinonitrile. In the application, the organic electrolyte is selected, and has good compatibility with the polymer gel skeleton and lithium salt, is not easy to separate out, and further has higher conductivity when used as an electrolyte.

In one example, the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer monomer to the volume of the organic electrolyte is (1 to 3): (0.1 to 5). It is understood that the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer-based monomer to the volume of the organic electrolyte may be selected from (1 to 3): (0.1 to 5). Specifically, the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer-based monomer to the volume of the organic electrolyte includes, but is not limited to, 1:0.1, 1:0.3, 1:0.5, 1:0.8, 1: 1. 1: 2. 1: 3. 1: 4. 1: 5. 2: 1. 2: 2. 2: 5. 3: 1. 3:3 or 3:5.

In one example, the organic electrolyte includes a volume ratio of 1: (0.9-1): (0.9-1) ethylene carbonate, dimethyl carbonate and diethyl carbonate.

In one example, the organic electrolyte includes a volume ratio of 1: (0.9 to 1.1) 1, 2-dimethoxyethane and 1, 3-dioxolane.

In one example, the organic electrolyte includes succinonitrile.

In one example, the organic electrolyte includes a volume ratio of 1: (0.9-1): (0.9-1) of ethylene carbonate, diethyl carbonate and methylethyl carbonate.

In a second aspect of the present application, there is provided a battery comprising a positive electrode, a separator, and a negative electrode, and an electrolyte filled in gaps of the positive electrode, the separator, and the negative electrode, the electrolyte being the gel polymer according to any one of examples of the first aspect of the present application.

In a third aspect of the present application, there is provided a method for manufacturing a battery according to any one of the examples of the second aspect of the present application, comprising the steps of:

a. mixing the unsaturated ester monomer, the oligomer monomer, the initiator and the lithium salt to prepare the precursor solution;

b. Assembling the positive electrode, the negative electrode, and the separator; injecting the precursor solution to assemble the battery cell;

c. Polymerizing the battery core at 40-80 ℃ to crosslink and copolymerize the saturated ester monomer and the oligomer monomer to form a polymer gel skeleton, so as to generate the gel polymer.

In one example, in the step a, the molar concentration of the lithium salt in the precursor solution is 0.5mol/L to 10mol/L. It is understood that the molar concentration of the lithium salt in the precursor solution includes, but is not limited to 0.6 mol/L、0.8 mol/L、1 mol/L、1.2 mol/L、1.4 mol/L、2 mol/L、3 mol/L、4 mol/L、5 mol/L、6 mol/L、7 mol/L、8 mol/L、9 mol/L or 10mol/L.

In one example, in step a, the precursor solution further includes an organic electrolyte; the ratio of the sum of the volumes of the unsaturated ester monomer and the polymer monomer to the volume of the organic electrolyte is (1-3): (0.1 to 5). It is understood that the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer-based monomer to the volume of the organic electrolyte may be selected from (1 to 3): (0.1 to 5). Specifically, the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer-based monomer to the volume of the organic electrolyte includes, but is not limited to, 1:0.1, 1:0.3, 1:0.5, 1:0.8, 1:1. 1: 2. 1: 3. 1:4. 1: 5. 2: 1. 2: 2. 2: 5. 3: 1. 3:3 or 3:5.

The following examples are further specific to illustrate the application in detail. It is also to be understood that the following examples are given solely for the purpose of illustration and are not to be construed as limitations upon the scope of the application, as many insubstantial modifications and variations are within the scope of the application as would be apparent to those skilled in the art in light of the foregoing disclosure. The specific process parameters and the like of the following examples are also merely examples of suitable ranges, i.e., those skilled in the art can make a suitable selection from the description herein without necessarily limiting the specific values of the examples.

The raw materials and corresponding English names used in the application are specifically as follows:

[ lithium salt ]

Lithium bis (trifluoromethane) sulfonyl imide: liTFSI;

Lithium hexafluorophosphate: liPF ₆;

lithium tetrafluoroborate: liBF ₄;

lithium bis (pentafluoroethyl) sulfonyl imide: liBETI;

lithium bis-fluorosulfonyl imide: liFSI;

lithium difluorooxalato borate: liDFOB;

[ unsaturated ester monomer ]

Ethylene carbonate: VEC;

Ethoxylated trimethylolpropane triacrylate: ETPTA;

vinylene carbonate: VC;

tetraethyleneglycol diacrylate: TEGDA;

methyl methacrylate: MMA;

pentaerythritol tetraacrylate: PETEA;

[ oligomer-based monomer ]

Polyethylene glycol methyl ether acrylate: PEGMEA;

Polyethylene glycol diacrylate: PEGDA;

polyethylene glycol dimethacrylate: PEGDMA;

polyethylene glycol dimethyl ether: PEGDME;

Polyethylene glycol divinyl ether: PEGDVE;

[ initiator ]

Azobisisobutyronitrile: AIBN;

dimethyl azodiisobutyrate: AIBME;

azodiisoheptonitrile: ABVN;

Bis (4-t-butylcyclohexyl) peroxydicarbonate: BBP;

Bis-lauroyl peroxide: LPO;

benzoyl peroxide: BPO;

[ organic electrolyte ]

Ethylene carbonate: EC;

dimethyl carbonate: DMC;

diethyl carbonate: DEC;

1, 2-dimethoxyethane: DME;

1, 3-dioxolane: DOL;

Succinonitrile: SN;

methyl ethyl carbonate: EMC.

Example 1

(1) And (3) manufacturing a positive electrode: active material LiFePO ₄ (LFP) was mixed with conductive agent Super P and binder polyvinylidene fluoride (PVDF) at 8:1:1, adding N-methyl pyrrolidone (NMP) to prepare anode slurry, coating the anode slurry on aluminum foil, drying the anode slurry, and cutting the anode slurry into pole pieces with the diameter of 12mm for later use;

(2) Preparing a precursor solution: liPF ₆ was dissolved in a volume ratio of 6:1 (number average molecular weight of about 200) and ETPTA, an initiator AIBN and an organic electrolyte were added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiPF ₆ is 1mol/L, and the volume ratio of the sum of the volumes of PEGDA and ETPTA to the volume ratio of the organic electrolyte is 1:5, the organic electrolyte is EC:DMC:DEC with the volume ratio of 1:1:1, and the mass percentage of the initiator in the precursor solution is 1wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 60℃for 2h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.87 mS/cm, the lithium ion migration number was 0.71, and the oxidation potential was 4.2V. Has excellent electrochemical properties.

The testing method of the polymer solid electrolyte comprises the following steps:

Ion conductivity test: and adding a precursor solution between two pieces of stainless steel, and polymerizing to form a structure that the gel polymer electrolyte is clamped between the two pieces of stainless steel, wherein the diameter of the stainless steel sheet is 15.8 mm, so that the stainless steel/gel polymer electrolyte/stainless steel symmetrical battery is formed. Electrochemical Impedance Spectroscopy (EIS) is performed by using an electrochemical workstation to measure the ion conductivity of the electrolyte, wherein the voltage amplitude is 10mV, and the frequency range is 0.1Hz-1MHz. And testing the ion conductivity of the electrolyte within the temperature range of 20-80 ℃. The cells were held at each test temperature for 30 minutes to reach thermal equilibrium prior to measurement.

Lithium ion migration number test: the Li/gel polymer electrolyte/Li symmetrical battery is composed, the lithium ion migration number of the electrolyte is measured by adopting an electrochemical workstation to carry out a chronoamperometric method, and a potentiostatic polarization process is carried out under a small potential (delta V) of 0.01V. At the same time, initial and steady state current values are recorded, and initial and steady state interface resistances before and after the polarization process are detected by impedance measurement, respectively.

Electrochemical stability window test: an electrochemical stability window of the gel polymer electrolyte was measured by using an electrochemical workstation to conduct a Linear Scanning Voltammogram (LSV), stainless steel was used as a working electrode, lithium was used as a counter electrode and a reference electrode, the scanning rate was 1.0mV/s, and from 2.0V to 6.0V vs. Li/Li ⁺.

Example 2

Example 2 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 2 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 1, and the specific steps are as follows:

(2) Preparing a precursor solution: liBF ₄ was dissolved in a volume ratio of 4:1 (number average molecular weight about 550) and VC, an initiator AIBME was added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiBF ₄ is 1: 1mol/L, and the mass percentage of the initiator in the precursor solution is 0.3wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left to stand at 50℃for 48 hours to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.2 mS/cm, the lithium ion migration number was 0.39, and the oxidation potential was 4.6V. Has excellent electrochemical properties.

Example 3

Example 3 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 3 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 1, and the specific steps are as follows:

(2) Preparing a precursor solution: liBETI was dissolved in a volume ratio of 4:1 (number average molecular weight about 250) and ETPTA, an initiator ABVN was added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiBETI is 1mol/L, and the mass percentage of the initiator in the precursor solution is 0.3wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left to stand at 50℃for 48 hours to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.36 mS/cm, the lithium ion migration number was 0.46, and the oxidation potential was 5.1V. Has excellent electrochemical properties.

Example 4

Example 4 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 4 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 1, and the specific steps are as follows:

(2) Preparing a precursor solution: liPF ₆ was dissolved in a volume ratio of 9:1 (number average molecular weight: about 480) and TEGDA, an initiator BBP was added thereto to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiPF6 is 10 mol/L, and the mass percentage of the initiator in the precursor solution is 0.5wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 60℃for 1h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 4.1 mS/cm, the lithium ion migration number was 0.55, and the oxidation potential was 5.2V. Has excellent electrochemical properties.

Example 5

Example 5 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 5 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 2, and the specific steps are as follows:

(2) Preparing a precursor solution: liFSI and LiPF ₆ were dissolved in a volume ratio of 4:1 (number average molecular weight of about 600) and ETPTA, an initiator LPO and an organic electrolyte were added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiFeSI is 1mol/L, the molar concentration of LiPF ₆ is 1mol/L, and the volume ratio of the sum of the volumes of PEGDA and ETPTA to the organic electrolyte is 2:1, the volume ratio of the organic electrolyte is 1:1:1, DMC and DEC, the mass percent of the initiator in the precursor solution being 2wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 60℃for 3 hours to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.56mS/cm, the lithium ion migration number was 0.72, and the oxidation potential was 4.7V. Has excellent electrochemical properties.

Example 6

Example 6 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 6 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 2, and the specific steps are as follows:

(2) Preparing a precursor solution: liDFOB was dissolved in a volume ratio of 1:2 (number average molecular weight of about 400) and VC, and adding an initiator AIBN and an organic electrolyte to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiDFOB is 2mol/L, and the volume ratio of the sum of PEGDA and ETPTA to the organic electrolyte is 1:4, selecting SN as an organic electrolyte, wherein the mass percentage of an initiator in a precursor solution is 1wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 60℃for 12h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.32mS/cm, the lithium ion migration number was 0.58, and the oxidation potential was 5.3V. Has excellent electrochemical properties.

Example 7

Example 7 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 7 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 2, and the specific steps are as follows:

(2) Preparing a precursor solution: liTFSI, liBETI was dissolved in a volume ratio of 3:1 (number average molecular weight of about 250) and MMA, an initiator BPO was added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiTFSI is 1mol/L, the molar concentration of LiBETI is 1mol/L, and the mass percentage of the initiator in the precursor solution is 0.1wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 80℃for 2h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.4mS/cm, the lithium ion migration number was 0.51, and the oxidation potential was 4.0V. Has excellent electrochemical properties.

Example 8

Example 8 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 8 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 2, and the specific steps are as follows:

(2) Preparing a precursor solution: liPF ₆ was dissolved in a volume ratio of 1:1 (number average molecular weight about 480) and PETEA, an initiator AIBN and an organic electrolyte were added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiPF ₆ is 1mol/L, and the volume ratio of the sum of the volumes of PEGDMA and PETEA to the organic electrolyte is 2:1, the organic electrolyte is selected from EC, DEC and EMC with the volume ratio of 1:1:1, and the mass percentage of the initiator in the precursor solution is 2 percent;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 60℃for 10 hours to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.76mS/cm, the lithium ion migration number was 0.43, and the oxidation potential was 4.4V. Has excellent electrochemical properties.

Example 9

Example 9 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 9 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 3, and the specific steps are as follows:

(2) Preparing a precursor solution: liBETI was dissolved in a volume ratio of 1: ETPTA and PEGDVE (number average molecular weight of about 250) of 4, and adding an initiator BPO to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiBETI is 1mol/L, and the mass percentage of the initiator in the precursor solution is 0.5wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 70℃for 2h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.59mS/cm, the lithium ion migration number was 0.62, and the oxidation potential was 4.5V. Has excellent electrochemical properties.

Example 10

Example 10 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 10 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 3, and the specific steps are as follows:

(2) Preparing a precursor solution: liPF ₆ was dissolved in a volume ratio of 1:9 and PEGDVE (number average molecular weight about 250), and an initiator BBP was added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiPF ₆ is 10mol/L, and the mass percentage of the initiator in the precursor solution is 0.5wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 70℃for 2h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 4.5mS/cm, the lithium ion migration number was 0.57, and the oxidation potential was 4.7V. Has excellent electrochemical properties.

Example 11

Example 11 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 11 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 3, and the specific steps are as follows:

(2) Preparing a precursor solution: liBETI was dissolved in a volume ratio of 1:4 and PEGDVE (number average molecular weight of about 250), an initiator LPO and an organic electrolyte SN were added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiBETI is 1mol/L, and the volume ratio of the sum of TEGDA and PEGDVE to the organic electrolyte is 2:1, the mass percentage of an initiator in a precursor solution is 1wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 70℃for 2h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.82mS/cm, the lithium ion migration number was 0.69, and the oxidation potential was 5.1V. Has excellent electrochemical properties.

Example 12

Example 12 is substantially the same as example 1, with the main difference that the preparation step of the precursor solution of step (2) of example 12 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 3, and the specific steps are as follows:

(2) Preparing a precursor solution: liPF ₆ was dissolved in a volume ratio of 1:2 (TEGDA and PEGMEA) (number average molecular weight about 2000), an initiator ABVN was added thereto to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiPF ₆ is 2mol/L, and the mass percentage of the initiator in the precursor solution is 0.5wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 40℃for 72h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.60mS/cm, the lithium ion migration number was 0.55, and the oxidation potential was 4.8V. Has excellent electrochemical properties.

TABLE 1

TABLE 2

TABLE 3 Table 3

Comparative example 1

Comparative example 1 is substantially the same as example 1, except that the preparation step of the precursor solution of step (2) of comparative example 1 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 1, and the specific steps are as follows:

(2) Preparing a precursor solution: liTFSI was dissolved in a volume ratio of 6:1 (number average molecular weight about 400) and VEC, initiator AIBN was added to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiTFSI is 1mol/L, and the mass percentage of the initiator in the precursor solution is 0.5wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left at 70℃for 2h to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.033mS/cm, the lithium ion migration number was 0.43, and the oxidation potential was 4.5V.

Comparative example 2

Comparative example 2 is substantially the same as example 1, except that the preparation step of the precursor solution of step (2) of comparative example 2 and the preparation step of the button cell of step (3) 2032 are different from example 1. The corresponding raw material composition is shown in table 1, and the specific steps are as follows:

(2) Preparing a precursor solution: liFSI is dissolved in a volume ratio of 1:5, adding an initiator AIBN and an organic electrolyte into PETEA and VC to prepare a precursor solution. Wherein, in the precursor solution, the molar concentration of LiFeSI is 3.2mol/L, and the volume ratio of the sum of PEGDA and ETPTA to the volume of the organic electrolyte is 10:3, the organic electrolyte is DME and DOL with the volume ratio of 1:1, and the mass percentage of the initiator in the precursor solution is 0.1wt%;

(3) Preparation of 2032 button cell: a lithium sheet was selected as the negative electrode, 60 μl of the precursor solution was injected into the polyolefin separator, and a 2032 coin cell was assembled. The cell was left to stand at 70℃for 5 hours to complete the polymerization. The ionic conductivity of the gel polymer electrolyte at room temperature was 0.17 mS/cm, the lithium ion migration number was 0.53, and the oxidation potential was 4.2V.

TABLE 4 Table 4

As can be seen from table 4, the precursor solution in comparative example 1 has a low content of oligomer-based monomer, thus resulting in the gel polymer electrolyte in comparative example 1 having a lower ionic conductivity than that of examples 1 to 8. In comparative example 2, although an organic electrolyte was added, two unsaturated ester monomers were selected for compounding, and an oligomer monomer was not added, resulting in a slightly lower ionic conductivity.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples merely represent a few embodiments of the present application, which facilitate a specific and detailed understanding of the technical solutions of the present application, but are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. It should be understood that, based on the technical solutions provided by the present application, those skilled in the art may obtain technical solutions through logical analysis, reasoning or limited experiments, which are all within the scope of protection of the appended claims. The scope of the patent of the application should therefore be determined with reference to the appended claims, which are to be construed as in accordance with the doctrines of claim interpretation.

Claims

1. A gel polymer, characterized in that the gel polymer comprises a polymer gel skeleton, a lithium salt and an initiator, wherein the polymer gel skeleton has a volume ratio of 1: (0.2-9) cross-linking and copolymerizing an unsaturated ester monomer and an oligomer monomer;

2. The gel polymer of claim 1, wherein the unsaturated ester monomer comprises one or more of ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, bis (trimethylolpropane) tetraacrylate, trimethylolpropane trimethacrylate, tetraethyleneglycol diacrylate, pentaerythritol tetraacrylate, and 2-phenoxyethyl acrylate;

The oligomer monomer comprises one or more of polyethylene glycol methyl ether acrylate and polyethylene glycol divinyl ether.

3. Gel polymer according to claim 1 or 2, characterized in that the polymer gel skeleton has a ratio by volume of 1: and (3) cross-linking and copolymerizing the unsaturated ester monomer and the oligomer monomer of (1-9).

4. Gel polymer according to claim 1 or 2, characterized in that the number average molecular weight of the oligomer-based monomer is 200-6000.

5. The gel polymer of claim 1 or 2, wherein the gel polymer has one or more of the following characteristics:

(1) The lithium salt comprises one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium bis (trifluoromethane) sulfonyl imide, lithium bis (pentafluoroethyl) sulfonyl imide;

(2) The initiator comprises one or more of azodiisobutyronitrile, azodiisoheptonitrile, dimethyl azodiisobutyrate, benzoyl peroxide, didodecyl peroxide and bis (4-tert-butylcyclohexyl) peroxydicarbonate;

(3) The mass fraction of the initiator in the gel polymer is 0.1% -3%.

6. The gel polymer of claim 1 or 2, further comprising an organic electrolyte having one or more of the following characteristics:

(1) The organic electrolyte comprises one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, 1, 2-dimethoxyethane, 1, 3-dioxolane and succinonitrile;

(2) The ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer monomer to the volume of the organic electrolyte is (1-3): (0.1 to 5).

7. A battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte filled in the gaps between the positive electrode, the separator, and the negative electrode, wherein the electrolyte is the gel polymer according to any one of claims 1 to 6.

8. A method of making a battery as defined in claim 7, comprising the steps of:

mixing the unsaturated ester monomer, the oligomer monomer, the initiator and the lithium salt to prepare a precursor solution;

9. The method for producing a battery according to claim 8, wherein the molar concentration of the lithium salt in the precursor solution is 0.5mol/L to 10mol/L.

10. The method for producing a battery according to claim 8 or 9, wherein the precursor solution further comprises an organic electrolyte; the ratio of the sum of the volumes of the unsaturated ester monomer and the oligomer monomer to the volume of the organic electrolyte is (1-3): (0.1 to 5).